The present invention relates to a tube for an observation device. For example, such an observation device may involve, for example, a microscope or similar device.
In a microscope, for example, an operating microscope, the distance of the object plane from the position of the equipment—exit pupil EP (AP) behind the eyepiece, thus the viewing level or eyepiece height, is determined by the equipment configuration of the system components of the microscope, which is dependent on the respective application.
For ergonomic reasons, of course, an individual adaptation of the viewing level to the body height of the user of the microscope, for example, of a surgeon, is extremely advantageous and thus desirable. In the often time-intensive working with the operating microscope, keeping the body of the surgeon relaxed is a very decisive factor for working without tiring.
In addition, it is a decisive factor not to modify disadvantageously the usual standard for the surgeon relative to basic optical parameters, such as, for example, the total magnification, the object-field diameter, the object resolution, the free working distance and the optical imaging quality when the viewing level is changed.
With respect to tubes with variable viewing levels, a large number of different solutions are already known in the prior art.
One proposal for solution, for example, contains a purely mechanical distance variation between the microscope body and the tube.
Another solution is described, for example, in DE 34 15 958 A1. A tube with variable viewing level for optical equipment is disclosed therein, whereby the tube can be rotated into two different positions. Of course, only two adjustments are possible, in which the tube can be swung in and locked. A linear displacement or variation of the tube is not provided.
Another solution results, for example, from EP 1 233 294 B1. In this patent, a switchable, thus stepwise variation of the viewing level is achieved by means of a tube construction with variable structural length. The mechanical variation of the structural length is produced in this case by a telescopically extendable region in the tube. The tube has a variable region in the convergent optical beam path for the change in the optical tube length, which is necessary for this, by displacing the focussing position of the intermediate image. In this variable region, correction lenses or groups of lenses which can be pushed in and out are utilized for varying the optical tube length in a first solution proposal, and correction lenses or groups of lenses which can be swung in and out are employed in a second solution proposal. These correction lenses have positive or negative refractive power and shift the intermediate image generated by the tube optics into the stationary viewing field of the eyepiece, whereby the diameter of the intermediate image, expressed in mm, is limited by the field-of-view number FN (SFZ), by a field stop introduced in the eyepiece. In this way, “approximately the same” image segment, visible and sharp, will be imaged in the eyepiece at the “desired” magnification.
In the described solution proposals, the intermediate image which is produced by the tube and displaced with the additional optics, will then be caused to coincide with the viewing field of the eyepiece by means of a mechanical change in distance in a telescopically extendable region.
In the purely mechanical lengthening of the afocal beam path between the components, with increasing change in distance, increasing vignetting also must be taken into account, thus a decrease in brightness from the center of the image field to the edge of the image field or even a cropping at the edge of the image field. In fact, in this approach to a solution, the basic optical parameters are not changed, but one must accept a more or less pronounced reduction in image quality due to the vignetting.
The high mechanical expenditure for the optical correction mechanism comprised of swung-in or pushed-in lenses must be viewed as an essential disadvantage of EP 1 233 294 B1. The space required for this is also problematical, since it leads to a clearly higher structural volume.
Another type of tube involves so-called “swing-in tubes”. Swing-in tubes are already known in and of themselves from the prior art. A swing-in tube for an optical observation apparatus, e.g., a microscope, is known, for example, from DE 197 07 520 A1. The swing-in tube provides a base part as well as an eyepiece support, wherein the swinging movement is executed by rolling the eyepiece support out onto the base part along an arc of a circle. A tilted mirror is provided mounted in a rotatable manner around an axis of rotation in the base part, whereby this tilted mirror is forcibly rotated by the roll-out movement of the eyepiece support on the base part. A tilted mirror mounted in a rotatable manner around an axis of rotation is likewise provided in the eyepiece support, whereby this tilted mirror also is forcibly rotated by the roll-out movement of the eyepiece support on the base part.
In this known solution, the swinging of the mirror is always coupled with the roll-out movement. In this way, the two mirrors each move while swinging under the same angle and are coupled with one another. The exit pupil can be swung in a swinging range of ±60° with the known solution. This swinging range that can be executed, however, is insufficient for many applications.
A swing-in tube is described in DE 103 16 242 A1, which can be swung by 180° and thus is named a 180° swing-in tube. For this purpose, the swing-in tube has a first optical element in the form of a prism, which can make an excursion out from a horizontal position by 45° to the top and to the bottom, respectively. Relative to this, another prism can simultaneously also move by 45° each time [to top and bottom] in a second axis. Together, the required angle of ±90° then results therefrom.
In many known solutions, the swing-in tube having a direct view is built too long, particularly for certain applications (for example, in neurosurgery, while in so-called face-to-face applications with a viewing angle (which is the diverging angle of the orthogonal line to the microscope axis) of 15° to 30°, the tube is built too short. Among other things, this means that the distance to the microscope axis is too short. The latter case particularly concerns applications in opthalmoscopy.